<!doctype html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>拍照2</title>
</head>
<script src="http://libs.baidu.com/jquery/2.1.4/jquery.min.js"></script>

<body>
<button id="take">拍照</button>
<br />
<video id="v" style="width: 640px;height: 480px;"></video>
<canvas id="canvas" style="display:none;"></canvas>
<br />
<img src="http://placehold.it/640&text=Your%20image%20here%20..." id="photo" alt="photo">
<script>
    !(function () {
        // 老的浏览器可能根本没有实现 mediaDevices，所以我们可以先设置一个空的对象
        if (navigator.mediaDevices === undefined) {
            navigator.mediaDevices = {};
        }
        if (navigator.mediaDevices.getUserMedia === undefined) {
            navigator.mediaDevices.getUserMedia = function (constraints) {
                // 首先，如果有getUserMedia的话，就获得它
                var getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;

                // 一些浏览器根本没实现它 - 那么就返回一个error到promise的reject来保持一个统一的接口
                if (!getUserMedia) {
                    return Promise.reject(new Error('getUserMedia is not implemented in this browser'));
                }

                // 否则，为老的navigator.getUserMedia方法包裹一个Promise
                return new Promise(function (resolve, reject) {
                    getUserMedia.call(navigator, constraints, resolve, reject);
                });
            }
        }
        const constraints = {
            video: true,
            audio: false
        };
        let videoPlaying = false;
        let v = document.getElementById('v');
        let promise = navigator.mediaDevices.getUserMedia(constraints);
        promise.then(stream => {
            // 旧的浏览器可能没有srcObject
            if ("srcObject" in v) {
                v.srcObject = stream;
            } else {
                // 防止再新的浏览器里使用它，应为它已经不再支持了
                v.src = window.URL.createObjectURL(stream);
            }
            v.onloadedmetadata = function (e) {
                v.play();
                videoPlaying = true;
            };
        }).catch(err => {
            console.error(err.name + ": " + err.message);
        })
        document.getElementById('take').addEventListener('click', function () {
            if (videoPlaying) {
                let canvas = document.getElementById('canvas');
                canvas.width = v.videoWidth;
                canvas.height = v.videoHeight;
                canvas.getContext('2d').drawImage(v, 0, 0);
                let data = canvas.toDataURL('image/webp');
                document.getElementById('photo').setAttribute('src', data);

                $.ajax(
                    {
                        type:"post",
                        url:"/abb",
                        dataType:"json",
                        data:{
                            src: $("#photo")[0].src
                        },
                        success:function(data){
                            alert("yeah!");
                        },
                        error:function(){
                            alert("请求失败");
                        }
                    }
                )
            }
        }, false);
    })();
</script>
</body>

</html>
